Insertion of catheters into the human body for therapeutic purposes carries the risk of infection which can, under certain circumstances, be life-threatening. For example, in the case of a urine drainage catheter inserted into the bladder via the urethra, this risk increases with the duration of catheterization and may be compounded by the presence of antibiotic-resistant microorganisms which are often endemic in hospital environments. Although the incidence of infection varies among hospitals, up to 45% of catheterized patients may acquire a urinary tract infection by three days of continuous catheterization. Catheter-induced urinary tract infections presenting as bacteriuria may resolve spontaneously on removal of the catheter or may require aggressive treatment with antibiotics and prolonged hospitalization. Severe cases may result in urethral scarring, kidney damage, or bacteremia, with corresponding morbidity and mortality. It has been estimated that of the 7.5 million patients per year who require indwelling urinary catheterizations, approximately 500,000 will acquire a catheter-associated urinary tract infection.* This results in an average of two additional days of hospitalization per infection, resulting in additional direct health care costs in excess of $500 million per year. Nosocomial urinary tract infections have been cited as the underlying cause of up to 56,000 deaths per year in the United States.* FNT *Platt, R.; Polk, B. F.; Murdock, B.; Rosner, B.; "Mortality Associated With Nosocomial Urinary-Tract Infection", The New England Journal of Medicine, 303 (1982) 638-642.
Potentially, the sleeved antimicrobial catheter of the present invention could be beneficial in any case where tubing must be inserted in the body. Obviously, such catheters will be most valuable in situations where infection is most likely. Aside from urinary catheterization, these situations generally involve artificial body openings. Examples of catheterization to which the teachings of the present invention could be advantageously applied include peritoneal dialysis catheters, hyperalimentation catheters, catheters associated with insulin delivery pumps, surgical drains, embolectomy catheters, cardiovascular catheters and intravenous catheters. For purposes of an exemplary showing, the teachings of the present invention will be described in terms of their application to a urethral catheter. This is a matter of convenience, only, and no limitation should be inferred therefrom except as stated in the claims hereinafter.
Prior art workers have developed numerous types of urethral catheters having associated means for antiseptic treatment of the urethra. U.S. Pat. No. 3,394,705 issued July 30, 1968 in the name of D. J. Abramson is exemplary. This reference teaches a drainage balloon catheter comprising two concentric tubes, one within the other. The inner tube constitutes a drainage tube. The outer tube is provided with a plurality of openings uniformly spaced in a spiral thereabout. Suction may be periodically applied to the outer tube for removal of infected matter from the urethra. Similarly, an antiseptic fluid may be injected through the outer tubing to irrigate the urethra and prevent spread of infection. U.S. Pat. No. 3,598,127, issued Aug. 10, 1971 in the name of James G. Wepsic, teaches a catheter comprising a nonpermeable drainage tube having a multiplicity of grooves formed in its periphery. The grooves are filled with a medicament and are covered with a sheath permeable by the medicament. Thus, each groove in the catheter constitutes a sort of non-replenishable medicament reservoir.
U.S. Pat. No. 3,981,299, issued Sept. 21, 1976 in the name of H. E. Murray, discloses a urethal catheter in the form of a triple lumen catheter having a highly porous rubber outer membrane for delivery of medication to the urethra. The drainage tube within the highly porous membrane is provided with a plurality of projections to properly space the membrane from the drainage tube. The catheter of this patent, like that of the above mentioned U.S. Pat. No. 3,394,705, is an irrigation device which does not provide diffusion and controlled release of the medicament. Finally, U.S. Pat. No. 4,186,745, issued Feb. 5, 1980 in the name of D. W. Lewis, discloses still another porous catheter comprised of a micropore structure which can be charged with certain substances that will minimize infections normally associated with the use of catheters. In one embodiment, the catheter is provided with a multiplicity of longitudinally extending passages spaced circumferentially about the catheter body and interconnected to one another by a circumferential passage through which a medicament can be introduced into the passage system. The catheter is made of porous material which allows the fluid retained therein to be released.
The controlled delivery of a medicament over a long period of time by diffusion through a membrane is not, per se, new. For example, U.S. Pat. No. 3,854,480, issued Dec. 17, 1974 to A. Zaffaroni describes a drug delivery system comprising a solid inner matrix material having solid particles of drug dispersed therethrough, surrounded by an outer polymeric membrane, insoluable to body fluids. Both the inner matrix material and the outer polymeric membrane are permeable to passage of the drug by diffusion, with the drug diffusing through the polymeric membrane at a lesser rate than through the solid inner matrix. However, such a structure would not be practical for catheters of the type contemplated herein.
In a urinary catheter wherein the reservoir is charged with an antimicrobial solution, the fluid antimicrobial agent preferably should be released along the entire length of the urethra from the meatus inward. This allows for attack of microbes already in the urethra at the time of catheterization as well as organisms that attempt to migrate into the space between the urethra and the catheter. The same principle is generally true in the use of non-urinary catheters. Ideally, the entire length that is inserted into the body should be capable of of delivering the fluid antimicrobial agent. In instances where a fluid antimicrobial agent is used to which internal tissues are less sensitive than external epithelial tissues, the sleeve should be of such length that it does not extend outside the body, or if it does, that portion of the sleeve extending outside the body can be coated with a material impervious to the fluid antimicrobial agent. Furthermore, the release of the fluid antimicrobial agent should not exceed that required for microbiocidal effacacy, since a greater release would have no beneficial effect.
Prior art catheters intended to dispense a fluid antimicrobial agent or other fluid material are frequently characterized by insufficient or uncontrolled release of the fluid material. Another problem lies in the fact that delivery of the fluid material is frequently asymmetric and non-uniform about the catheter or non-uniform throughout the length of that much of the catheter in contact with the body. Often, antimicrobial action of the catheter is of limited duration and without provision for replenishment.
The catheter structure of the present invention provides a concentric, replenishable fluid antimicrobial agent reservoir about the shaft or drainage tube of the catheter. The antimicrobial agent in the fluid material is dispensed by diffusion through the sleeve. The release rate of the fluid antimicrobial agent can be varied conveniently by adjusting the concentration of the fluid antimicrobial agent and the composition and thickness of the sleeve. The provision of longitudinally extending capillary grooves upon the inside surface of the sleeve will assure uniform distribution of the fluid antimicrobial agent throughout the length of the sleeve; will hold the fluid antimicrobial agent at the surface of the sleeve; will assure availablity of the fluid antimicrobial agent to areas where the sleeve is held intimately against the drainage tube of the catheter; and will help prevent adhesion of the sleeve to the drainage tube of the catheter.